Method for continuous extrusion of metals



May 7, 1963 METHOD FOR CONTINUOUS EXTRUSION 0F METALS Filed Dec. 25, 1959 FIG. 2

INVENTOR. SVEN BOTES UMIYWMM ATTORNEYS s. R. BOTES 3,088,589

United States Patent 3,088,589 METHOD FOR CONTINUOUS EXTRUSION 0F METALS Sven R. Botes, Spanga, Sweden, assignor to John Robertson Co., Inc., Brooklyn, N.Y., a corporation Filed Dec. 23, 1959, Ser. No. 861,602 Claims priority, application Sweden Jan. 10, 1959 2 Claims. (Cl. 207-) The present invention relates to a method for continuous extrusion of metals, such for example as electric cable lead sheathing, and more particularly sheathing of pure lead or lead alloyed with some elements such as tin, antimony, arsenic, calcium and tellurium.

Generally continuously operating extruders, comprising a propelling screw rotating in a screw housing to expel the metal, are used for metals of the character here of concern. The extruder may be fed for example with molten metal through a pipe line from a melting pot under high pressure to a suitable die, the molten metal being cooled to a solid or plastic state by the time it arrives at the die by a suitable cooling medium circulating in channels arranged in the screw housing, the screw or both of them.

By general experience it has been found that although such extrusion apparatus may perform acceptably well over a period of time, ultimately there is a reduction in the performance thereof, which is believed to result at least in part by a coating or deposition of contaminants in the metal onto those portions of the extruder proper in contact with the extruded metal. It appears quite probable that the deposited contaminants have an adverse elfect upon that heat transfer-from the extrusion metal in the space between the usual screw and housing to cooling channels in the apparatus-which is necessary for conversion of molten metal to a plastic condition at the required rate.

By the present invention these difliculties are obviated by an at least intermittent feeding to an extrusion apparatus of what may be termed a lubricant, or a substance favorably alfecting chemically a coating of the type discussed, such as stearic acid, oleic acid, sodium stearate, lithium stearate, or a mixture of two of such substances.

It is to be understood that such substances are named only as examples of effective materials, and that a plurality of other similar acids or their compounds may be used advantageously, as well as other materials with ability to split olf similar acids in the extruder. These acids or materials can be used either in their ordinary state or dissolved in some solvent. Lubricants and/or chemically active materials of the character described can be supplied through channels arranged for this purpose in the wall of the screw housing or in the screw or in both of these apparatus elements.

Another successful approach to the problem has been to use the molten metal feed tube as a conduit for introducing the lubricant or coating-counteracting substance or mixture to the extrusion apparatus; in which case means may be utilized to feed the molten metal or the introduced substance alternately to the apparatus.

An example of an application of the invention is illustrated in the accompanying drawing in which:

FIG. 1 is a schematical elevation view of an apparatus for extrusion according to the present invention,

FIG. 2 is an enlarged view partly in section illustrating one form of the lubricant feeding device;

FIG. 3 is an enlarged view partly in section, illustrating another form of lubricant feeding device.

In FIG. 2 is shown the feed pipe 3 for molten metal,

3,088,589 Patented May 7, 1963 a valve 6 with a lever for hand operation and a reservoir 7 for the lubricant or counteracing material. The outlet of valve 6 is in communication with the interior of feed pipe 3 and is secured thereto by a nipple screwed in a threaded aperture 9 in the wall of the pipe, and sealed by a copper gasket 8. In FIG. 3 a removable sealing plug 10, also sealed by a copper gasket 8, is screwed into a threaded hole 9 in the wall of the feed pipe 3.

One manner of carrying out the method according to the invention, which has been used successfully consists in cutting ofi? the supply of molten metal for some time to the feed pipe 3 by closing the valve inside the melting pot 1 of FIG. 1 by means of valve handle 2. Since the screw of the extruder 5 is rotating a vacuum will be created inside pipe 3 and this vacuum is utilized for introducing into the pipe coating-counteracting or inhibiting material of the character described through the lubricant feeding device shown generally at 4. Where such is used in a liquid form or in a solution, an arrangement according to FIG. 2 is preferable and the material is then introduced into the pipe 3 by opening the valve 6 for some moments after the molten metal supply is cut off.

However, in the event that the coating inhibiting or counteracting material should be in the solid state, for instance in the shape of a stick, or if it should be comprised of a powder or granules, then an arrangement according to FIG. 3 will be preferable; in which case the sealing plug 10 is simply removed for the time necessary to introduce the material into the pipe 3. Then upon opening the valve inside the melting pot again the material is carried into the extruder by the molten metal.

I claim:

1. In a method for extruding metal comprising: alternately introducing molten metal and a lubricant of material selected from the group consisting of stearic acid, sodium stearate, lithium stearate, or a mixture of two of the aforesaid materials into the feed path to an extruder, cooling the metal to a plastic state, and thereafter extruding the metal.

2. The method of converting molten metal to a plastic condition in extrusion apparatus at a required rate for subsequent extrusion comprising: introducing molten metal into the feed path to the extrusion apparatus, intermittently stopping the introduction of molten metal and introducing lithium stearate into said feed path; cooling the metal to a plastic state; and thereafter extruding the metal.

References Cited in the file of this patent UNITED STATES PATENTS 1,466,125 Faupel Aug. 28, 1923 2,038,215 Gillis Apr. 21, 1936 2,047,237 Updegrafi July 14, 1936 2,741,567 Otto Apr. 10, 1956 2,840,890 Emm July -1, 1958 2,870,903 Le Due Jan. 27, 1959 2,884,129 Ljunberg Apr. 28, 1959 2,921,865 Kubie Jan. 19, 1960 2,921,874 Kubie Jan. 19, 1960 FOREIGN PATENTS 336,291 Germany Apr. 27, 1921 OTHER REFERENCES Lubrication in the Drawing of Metals, by Samuel Spring, reprinted from Steel, received in Library Aug. 12, 1946, pp. 19-25. 

1. IN A METHOD FOR EXTRUDING METAL COMPRISING: ALTERNATELY INTRODUCING MOLTEN METAL AND A LUBRICANT OF MATERIAL SELECTED FROM THE GROUP CONSISTING OF STEARIC ACID, SODIUM STEARATE, LITHIUM STEARATE, OR A MIXTURE OF TWO OF THE AFORESAID MATERIALS INTO THE FEED PATH TO AN EXTRUDER, COOLING THE METAL TO A PLASTIC STATE, AND THEREAFTER EXTRUDING THE METAL. 